must broadcast network name to connect

[Default User]

Okay, I am stumped. 

Using Ubuntu 7.04 (no special or exotic setup), I can connect
automatically to my DSL modem/router if the "network name" (aka SSID,
aka ESSID) is broadcast, whether encryption is on or off.  

But if the network name, for example 93PRINCETON97 is NOT broadcast,
Network Manager will not connect, whether encryption is on or off.
Clicking the Network Manager Icon shows the signal bar graph for the
router, with a sufficient signal, but a blank space where the network
name would be if broadcast. 

I have tried cicking the blank name bar graph, clicking the Network Name
icon and entering in the dialog box the network name in uppercase and
lowercase, with and without single and double parentheses, with
parentheses and blank spaces, and even left it completely blank, etc.
Each time, Network Manager "searches" for about 30 seconds and then
gives up. 

I could just leave the network name set to always broadcast by default,
but for security reasons I do not want to broadcast it at all, and
should not have to. 

Does anyone know why the only way to connect is to broadcast the network
name?